In the proposed research, the influence of the type of fatty acid incorporated into phospholipids on the enzymatic functions of membrane bound enzymes will be studied. The phospholipids will consist of C14 labeled 1,2 distearyl and 1,2 dioleyl (cis or trans) phosphatidylcholine in which the fatty acid on the beta-position will be increasingly unsaturated from oleic to arachidonic acid. A model system will be used, initially, endoplasmic reticulum from rat liver preparations. Freeze dried preparations from rat liver will be delipidated with n- butanol at -20 degrees C and subsequently relipidated with the synthetically prepared phospholipids. These relipidated preparations will be used for the investigation of the kinetic parameters and activation energies for various enzyme systems such as glucose-6-phosphatase and acyl-CoA synthetase. The synthetic phospholipids will also be used in a systematic in vitro study of the thermal transmission points of mixtures of phospholipids in isotonic solution. These studies should add to present knowledge on the influence of the cis and trans isomeric unsaturated fatty acid chains in phospholipids on the enzymatic functions of membrane bound enzymes and their possible influence on cell membrane structure. The methods that will be used to synthesize and characterize the phospholipids will be similar to those that have been used in previous publications.